As an example, the loss of DNA methylation in three CpG loci in the intron 1 of the triggering receptor expressed on myeloid cells 2 gene (TREM2, an Alzheimer’s disease susceptibility gene) results in a higher expression of TREM2 in leucocytes of Alzheimer’s patients [62]. This evidence concerns the gene TREM2 and early-onset autosomal dominant Alzheimer disease.